The present invention relates to an ink wiping device for wiping or scraping off excess ink from the plate surface in an intaglio rotary printing machine.
In intaglio printing, ink is applied by an inking device to the intaglio printing plate wrapped around a intaglio cylinder, and excess ink on the non-printing areas of the intaglio printing plate is removed by a wiping roller which rotates against the intaglio printing plate, leaving ink only in the grooves cut in the intaglio printing plate according to a pattern to be printed. For making a print, a sheet of paper is fed between the plate cylinder and an impression cylinder pressed thereagainst to allow the ink to be transferred from the pattern grooves onto the sheet of paper. The ink wiping roller is rotatably immersed in a cleaning solution such as trichlorethylene contained in a tank. A plurality of brushes extend axially along the ink wiping roller in contact with the circumferential surface of the ink wiping roller in the cleaning solution. The ink as it is wiped off the intaglio printing plate and transferred to the wiping roller is removed from the latter by the brushes and the cleaning solution, and dissolved into the cleaning solution in the tank.
Various brush and scraper constructions are known for use in the ink wiping device. One form is composed of a plurality of rows of brushes fixed to a bracket disposed below the ink wiping roller and having brush ends held against the circumferential surface of the ink wiping roller. Another construction comprises a circular brush rotatably held against the ink wiping roller. According to still another proposal, the ink is wiped off by a scraper of hard rubber placed against the ink wiping roller. The fixed and rotatable brushes however are disadvantageous in that their ends contacting the ink wiping roller remain coarse in density and cannot wipe off the ink sufficiently as linear brush marks are left on the ink wiping roller as it rotates, a limitation which could not be eliminated if the bristles were denser. The brushes are forced to bend at all times in the direction of rotation of the ink wiping roller, and tend to be less resilient and thus wear rapidly, with the results that the brushes will prove less durable and less stable in operation. The rotatable brushes have additional difficulties in that they are more liable to retain dirt, they are difficult to serice and they agitate the cleaning solution which becomes turbid and ends up with reduced cleaning power. With the scraper, the cleaning solution is less effective to clean the ink wiping roller when the scraper scrapes the ink off the ink wiping roller. To cope with this, it is necessary that scrapers be located at different positions around the ink wiping roller along the direction of rotation thereof. However, it would be highly costly to do so, and moreover there is insufficient space to accommodate a plurality of scrapers.